如何从linq查询中检索聚合值？

Question

我有以下查询：

from spl in SpeciesLists 
         join ar in Areas on spl.Station.Area equals ar.Id 
         join ground  in Grounds on ar.Ground equals ground.Id 
         join re in Regions on ground.Region  equals re.Id 
         where spl.Station.Trip.year ==2013
         select new 
           {
              SpciesCommonName = slp.Description,
              Are = ar.description,
              Ground = ground.Code,
              NumberOfTripsInProtectedAreas = "To be calculated",
           }

“旅行”可以包括一个或多个站。保护区域可在Trip表中找到，可以是1或0.一个站点有一个或多个物种。

如何计算保护区的行程次数？

非常感谢提前

Answer 1

您需要在where子句中添加ProtectedArea == 1的条件。

同样如您的评论所述，该小组将通过：slp.Description，ar.description和 ground.Code

以下是代码：

from spl in SpeciesLists 
             join ar in Areas on spl.Station.Area equals ar.Id 
             join ground  in Grounds on ar.Ground equals ground.Id 
             join re in Regions on ground.Region  equals re.Id 
             where spl.Station.Trip.year ==2013
             && spl.Station.Trip.ProtectedArea == 1
             group spl by new { slp.Description, ar.description, ground.Code } into Result
             select new 
               {
                  SpciesCommonName = Result.Key.Description,
                  Are = Result.Key.description,
                  Ground = Result.Key.Code,
                  NumberOfTripsInProtectedAreas = Result.Count()
               }